To attract, repel, or trap arthropods such as insects, mosquitoes, chiggers, flies, fleas, and ticks, systems typically take advantage of their specific behaviors of search, locate, or avoidance. Mosquitoes in particular have a sophisticated array of means and behavior to locate their prey and avoid hazards.
Mosquitoes can detect distant carbon dioxide emissions and moisture. Over 50 chemicals, such as octanol, and lactic acid, have been identified as attractants to mosquitoes and presumably have been used as chemical signatures of their prey. Mosquitoes can detect the warm surfaces of their prey and can distinguish between cold and hot surfaces and avoid those that are not within typical body temperatures of their prey. They are attracted to contrasting and colored surfaces and are attracted to light, including infrared. It is reported that they are attracted to sounds and motion and will be disturbed by flashes of light, sounds, vibrations, and wind.
Typical mosquito repellents, such as N,N-diethyl-3-methylbenzamide (DEET), in most cases, have been found to simply interfere with the mosquito's sensors impairing their ability to track carbon dioxide and presumably other scents also. There is some evidence that DEET and other chemicals on or absorbed by the skin kill parasites that have been injected by the insects or arthropods. But ultimately DEET, on the skin and sound repellents have not prevented some of the insects from finding skin and subsequently stinging. When DEET is applied to the skin between 5.6% and 15% will be absorbed through the skin and into the blood stream of the user.
The effects of repellents are generally to act as an anesthetic; they should not be ingested or applied to open wounds and in excessive cases, topical application has lead to death.